MYSQL使用where子句选择查询

I have the table

我有桌子

    
itemuid    |    category
-----------------------------
1          |    3
2          |    3
3          |    21
4          |    3
5          |    3
6          |    21
7          |    3
-----------------------------

I now want to select the itemuid with the category 21 before itemuid 5. The itemuid is the only information I've got from which I need to search backwards.

我现在想要在itemuid 5之前选择类别为21的itemuid .siteuid是我从中获得的唯一信息，我需要向后搜索。

Can anyone tell me how the select and where query must look like? Thanks.

任何人都可以告诉我如何选择和查询必须是什么样子？谢谢。

6 个解决方案

#1

SELECT * FROM table
  WHERE itemuid < 5 AND category = 21
  ORDER BY itemuid DESC
  LIMIT 1

#2

SELECT itemuid from notablenameinquestion where category=21 AND itemuid < 5 order by itemuid LIMIT 1;

#3

    SELECT s.itemuid
    FROM (SELECT itemuid
          FROM yourTable 
          WHERE yourConditions  
          ORDER BY category DESC) s
    WHERE ROWNUM =   1

#4

If i understand you correctly:

如果我理解正确的话：

Select Top(1) itemid from table_name where categoryid=21 and itemid<5

#5

-1

If "before" means the biggest itemuid that is still smaller than 5, then:

如果“之前”表示仍然小于5的最大项目，则：

select max(itemuid) from tablename where itemuid < 5 and category = 21

#6

-2

If I'm understanding you correctly, this should work:

如果我正确理解你，这应该有效：

SELECT itemuid FROM table_name WHERE category=21 and itemuid < 5

#1

SELECT * FROM table
  WHERE itemuid < 5 AND category = 21
  ORDER BY itemuid DESC
  LIMIT 1

#2

SELECT itemuid from notablenameinquestion where category=21 AND itemuid < 5 order by itemuid LIMIT 1;

#3

    SELECT s.itemuid
    FROM (SELECT itemuid
          FROM yourTable 
          WHERE yourConditions  
          ORDER BY category DESC) s
    WHERE ROWNUM =   1

#4